Vol. 60, 2021

(update: 2021.01.21; 03.08)
 

Differential Protein Metabolism and Regeneration in Gastrocnemius Muscles in High-fat Diet Fed Mice and Pre-hibernation Daurian Ground Squirrels: A Comparison between Pathological and Healthy Obesity

Xia Yan^1,2,§, Qiaohua Niu^2,§, Xuli Gao^1,2, Shenyang Shen², Nan He², Huiping Wang^1,2, Rongrong Fang², Yunfang Gao^1,2,*, and Hui Chang^1,2,*

¹Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi'an, 710069, P.R. China. *Correspondence: E-mail: changhui@nwu.edu.cn (Chang); gaoyunf@nwu.edu.cn (Y. Gao). Tel: +8615389060926. Fax: 029-88303572.
E-mail: 2364348698@qq.com (Yan); 672622062@qq.com (X. Gao); wanghp@nwu.edu.cn (Wang)
²Key Laboratory of Resource Biology and Biotechnology in Western China (College of Life Sciences, Northwest University), Ministry of Education, Xi'an, 710069, P.R. China. E-mail: 1906266475@qq.com (Niu); 2232856399@qq.com (Shen); 1059006214@qq.com (Fang)

^§XY and QN contributed equally to this work.
Received 27 May 2020 / Accepted 31 December 2020
Communicated by Pung-Pung Hwang

We focused on pathological obesity induced by excessive fat intake (nutritional obesity) in non-hibernator and healthy obesity due to pre-hibernation (PRE) fat storage in hibernator to study the effects of different types of obesity on skeletal muscle protein metabolism and cell regeneration. Kunming mice were fed with high-fat diet for 3 months to construct a pathological obesity model. Daurian ground squirrels fattened
naturally before hibernation were used as a healthy obesity model. Body weight, adipose tissue wet weight, gastrocnemius muscle wet weight, muscle fiber cross-sectional area (CSA) and fiber type distribution were measured. The protein expression levels related to protein degradation (MuRF-1, atrogin-1, calpain1, calpain2, calpastatin, desmin, troponin T, Beclin-1, LC3-II), protein synthesis (P-Akt, P-mTORC1, P-S6K1,
P-4E-BP1) and cell regeneration (MyoD, myogenin, myostatin) were detected by Western blot. As a result, the body weight and adipose tissue wet weight were both significantly increased in high fat obese (OB) mice and pre-hibernation fat (PRE) ground squirrels. The muscle wet weight, ratio of muscle wet weight to body weight, and muscle fiber CSA were significantly decreased, while the percentage of MHC I fiber isoform was significantly increased in gastrocnemius muscle of OB mice compared with the control (CON) group. The protein expression levels of P-Akt, P-mTORC1, P-4E-BP1 and myogenin were significantly decreased, while those of calpain1, calpain2, MuRF-1 and myostatin were significantly increased in the OB mice. In the ground squirrels, the muscle wet weight, muscle fiber CSA and percentage of MHC I fiber isoform all showed no change in the gastrocnemius muscle in the PRE group compared with the summer active (SA) group. The protein expression levels of P-Akt, P-mTORC1, P-S6K1 and MyoD were significantly increased, while those of Beclin-1 and LC3-II were significantly decreased in the PRE
ground squirrels. This study demonstrated that the decrease in protein expression levels in the Akt/mTOR pathway (P-Akt, P-mTORC1 and P-4E-BP1) and cell regeneration (myogenin) and the increase in protein expression levels of the calpain pathway (calpain1 and calpain2) and ubiquitin-proteasome pathway (MuRF-1) were involved in the mechanism of muscle atrophy in gastrocnemius muscle of the pathologically obese Kunming mice induced by high-fat diet. In contrast, the increased protein expression levels of the Akt/mTOR pathway (P-Akt, P-mTORC1 and P-S6K1) and cell regeneration (MyoD), and the decreased protein expression levels of the autophagy lysosomal pathway (Beclin-1 and LC3-II) were involved in the mechanism of anti-atrophy in gastrocnemius muscle of the healthy obese ground squirrels fattened before hibernation.

Key words: High-fat diet, Pre-hibernation fattening, Protein metabolism, Cell regeneration, Skeletal muscle atrophy.

Citation: Yan X, Niu Q, Gao X, Shen S, He N, Wang H, Fang R, Gao Y, Chang H. 2021. Differential protein metabolism and regeneration in gastrocnemius muscles in high-fat diet fed mice and pre-hibernation Daurian ground squirrels: a comparison between pathological and healthy obesity. Zool Stud 60:6. doi:10.6620/ZS.2021.60-06.